I've just had an email from Airline Network (
Cheap Worldwide Flights and cars, Discount Hotels, Bargain Holidays to Dubai, America, Australia and Thailand ) with offers on some EVA flights heathrow-Bangkok for £449
The offer is from late March '08 until sometime in June, although for the dates at the end of March there are only a few dates available.
There's also London-Singapore-Phuket with Singapore Airlines for £565, but I have not checked the dates on these.